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<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Hi Kcc,<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Thank your advices.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal">>Start from switching from inline instrumentation to instrumentation with calls: <o:p></o:p></p>
<p class="MsoNormal">>With Clang that is "-mllvm -asan-instrumentation-with-call-threshold=0", gcc should have something similar. <o:p></o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I see the call-threshold option force to use the calls and have same effect as -fsanitize=kernel-address in below code. Thanks.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><a href="http://llvm.org/svn/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp">http://llvm.org/svn/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp</a><o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">line 1956:<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> bool UseCalls =<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> CompileKernel ||<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> (ClInstrumentationWithCallsThreshold >= 0 &&<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> ToInstrument.size() > (unsigned)ClInstrumentationWithCallsThreshold);<o:p></o:p></span></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal">>Obviously, there is a cost in performance. <o:p></o:p></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">The call cost to my firmware should be very low. (1) Not like CPU-intensive application, my firmware is
an IO-intensive software, the boot performance bottleneck is usually because of slow IO response. If Asan instrumentation mainly bring overhead to CPU, it is not a big problem to my firmware. (2) Not like memory-intensive application, my firmware usually have
sufficient system memory to use. If Asan mainly bring overhead to system memory consumption for shadow memory metadata, it is not a big problem for me too.
<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">But my firmware usually care the code size, even in debug version. If my Asan-enabled firmware image size
is too big, I cannot easily apply and run it on real HW.<o:p></o:p></span></p>
<p class="MsoNormal"><span style="color:#1F497D"> <o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal">>Clang (and recent gcc) also have a convenience flag -fsanitize=kernel-address:<o:p></o:p></p>
<p class="MsoNormal"><span class="gmail-apple-tab-span">> </span>movq<span class="gmail-apple-tab-span">
</span>%rdi, %rbx<o:p></o:p></p>
<p class="MsoNormal"><span class="gmail-apple-tab-span">> </span>callq<span class="gmail-apple-tab-span">
</span>__asan_load4_noabort<o:p></o:p></p>
<p class="MsoNormal"><span class="gmail-apple-tab-span">> </span>movl<span class="gmail-apple-tab-span">
</span>(%rbx), %eax<o:p></o:p></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">I like the
</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">-fsanitize=kernel-address option, and I believe it better fit my firmware scenario rather than -fsanitize=address. I but after take a look at the current LLVM Asan implementation,
I have some concerns that kernel-address might disable the global and stack instrumentations by default as below code. Does LLVM Asan really support -fsanitize=kernel-address to check glabal and stack buffer issues?</span><o:p></o:p></p>
<p class="MsoNormal"><o:p> </o:p></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><a href="http://llvm.org/svn/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp">http://llvm.org/svn/llvm-project/llvm/trunk/lib/Transforms/Instrumentation/AddressSanitizer.cpp</a><o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">line 1723:<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> // TODO(glider): temporarily disabled globals instrumentation for KASan.<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> if (ClGlobals &&
</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:red">!CompileKernel</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">) {<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> Function *CtorFunc = M.getFunction(kAsanModuleCtorName);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> assert(CtorFunc);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> IRBuilder<> IRB(CtorFunc->getEntryBlock().getTerminator());<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> Changed |= InstrumentGlobals(IRB, M);<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> }<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Line2287:<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> bool DoStackMalloc = ClUseAfterReturn &&
</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:red">!ASan.CompileKernel
</span><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">&&<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"> LocalStackSize <= kMaxStackMallocSize;<o:p></o:p></span></p>
<p class="MsoNormal" style="text-align:justify;text-justify:inter-ideograph"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D"><o:p> </o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Thanks<o:p></o:p></span></p>
<p class="MsoNormal"><span style="font-size:11.0pt;font-family:"Calibri",sans-serif;color:#1F497D">Steven<o:p></o:p></span></p>
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